Provided are a radio communication mobile station apparatus, a radio communication base station apparatus and a radio communication method, which make it possible to correctly switch between transmission modes for a PUSCH and a PUCCH while impeding signaling overhead from increasing. A transmission mode setting unit (107) detects an instruction given by a base station, the instruction indicating a multiplexing method for a PUSCH and a PUCCH. A trigger information reporting determination unit (108) performs threshold discrimination where PHR_pucch, which is calculated by PHR_control calculation unit (106), is compared with a threshold value that depends on the multiplexing method indicated by the instruction given by the base station. Specifically, in a TDM transmission mode, trigger information is reported if PHR_pucch>X1[dBm] is satisfied. On the other hand, in an FDM transmission mode, the trigger information is reported if PHR_pucch